1. Field of the Invention
Various embodiments of the present invention relate to weighted waveforms for improved jam code effectiveness.
In various examples, weighted waveforms for improved jam code effectiveness may be implemented in the context of systems, methods, computer program products and/or algorithms.
2. Description of Related Art
Infrared (IR) guided surface-to-air missiles typically work by detecting emitted IR radiation from a target. IR energy is collected by a spinning gyroscopic telescope and is modulated by a complex reticle. This modulated energy is collected by an IR sensitive detector and is used to generate a time-varying electrical signal. This signal has features (e.g., amplitude and/or frequency) which are proportional to the pointing error angle between the gyroscopic telescope and the target in question.
The detected signal is typically processed through two electrical control loops. The first loop is commonly referred to as the “track” loop and is used to maintain the pointing of the gyroscopic telescope. The track loop acts to reduce the measured error angle between the gyroscopic telescope and the target. The second loop is commonly referred to as the “guidance” loop and is used to maintain the pointing of the missile body. The guidance loop acts to steer the missile body to a predicted intercept point based on the perceived target motion.
In the employment of directable IR laser countermeasures, a laser is aimed into the missile's gyroscopic telescope and the laser light is modulated in such a way as to emulate the error signal of the missile. Using a higher laser power and stray-light paths, the laser light is able to generate a more powerful signal than the true error signal associated with the target. This countermeasure signal is used to steer the missile's gyroscopic telescope to a position where the gyroscopic telescope can no longer see the target. A missile which has been commanded to look at a position other than the target is said to be in a condition of optical break lock (“OBL”). OBL is typically the primary defeat mechanism for modern laser jammers and frequencies.
Frequencies in modern OBL jam codes are typically selected based on the “spin” frequency of the missile's gyroscopic telescope. That is, the frequencies used in the jam codes are selected to match the best guess of the current spin rate of the missile's gyroscopic telescope. This produces straight line motion from the missile head and generates the fastest OBL possible. A significant complexity to this scenario is the variance in gyroscopic telescope spin frequency within each specific missile type. A particular class of missiles can have spin frequency variation within a band of operation due to manufacturing error tolerances; a missile can also have a variance of an ever greater degree specifically by the design of the missile itself. The latter is a scenario presenting a greater challenge, as this variance will typically cover a far greater frequency band, and will typically be a function of the missile flight profile.
Of note, at any given time, the correct frequency with which to jam a missile is the frequency at which the missile telescope is currently spinning. Given the ambiguity in missiles with variable frequencies, conventional code typically covers at least the entire design range of the missile spin rates; however, only a small portion of such conventional code is typically truly effective (from a conventional design point of view a difficulty has arisen because it has not been known which part of code is the effective part for an arbitrary engagement).
FIG. 1 shows a block diagram of a conventional interaction between an IR seeking missile and a countermeasure system installed on a target. As seen in this figure, missile 101 includes seeker head 101A (having therein a spinning gyroscopic telescope). The seeker head 101A detects emitted IR radiation from a target 103 (e.g., an aircraft or the like). Further, countermeasure system 105 includes laser 105A, which sends laser light (not necessarily visible) to the missile's gyroscopic telescope.
FIG. 2 shows a block diagram of a conventional effect on a missile's gyroscopic telescope spin frequency as a result of the missile's spin (which may change, for example, at different times in the missile's flight profile). As seen in this figure (which is taken from the perspective of looking head-on into missile 201) if, for example, the missile's gyroscopic telescope 203 is rotating clockwise at a spin frequency of X, and the missile 201 itself is rotating counterclockwise at a spin frequency of Y, the effective spin frequency of the gyroscopic telescope 203 is X-Y. Of course, rotation in the same direction would be additive.